Network Working Group M. Mealling
Request for Comments: 3553 VeriSign
BCP: 73 L. Masinter
Category: Best Current Practice Adobe Systems
T. Hardie
Qualcomm
G. Klyne
Nine by Nine
June 2003
An IETF URN Sub-namespace for Registered Protocol Parameters
Status of this Memo
This document specifies an Internet Best Current Practices for the
Internet Community, and requests discussion and suggestions for
improvements. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This document describes a new sub-delegation for the 'ietf' URN
namespace for registered protocol items. The 'ietf' URN namespace is
defined in RFC 2648 as a root for persistent URIs that refer to
IETF-defined resources.
1. Introduction
From time to time IETF standards require the registration of various
protocol elements in well known central repository. The Internet
Assigned Numbers Authority maintains this central repository and
takes direction from the IETF on what, how and when to add items to
it. The IANA maintains lists of items such as all assigned port
numbers, MIME media types, enterprise numbers, etc.
Over time there has developed a need to be able to reference these
elements as URIs in various schema. In the past this was done in a
very ad hoc way that easily led to interoperability problems. This
document creates a new sub-delegation below the "ietf" [2]URN
namespace [1] called 'params' which acts as a standardized mechanism
for naming the items registered for IETF standards. Any assignments
below that are specified in an RFC according to the IETF consensus
process and which include the template found in Section 4.
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RFC 3553 IANA URN Namespace June 20032. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119.
3. IETF Sub-namespace Specifics
Sub-namespace name:
params
Declared registrant of the namespace:
The Internet Engineering Task Force
Declaration of structure:
The namespace is primarily opaque. The IANA, as operator of the
registry, may take suggestions for names to assign but they
reserve the right to assign whatever name they desire, within
guidelines set by the IESG. The colon character (":") is used to
denote a very limited concept of hierarchy. If a colon is present
then the items on both sides of it are valid names. In general,
if a name has a colon then the item on the left hand side
represents a class of those items that would contain other items
of that class. For example, a name can be assigned to the entire
list of DNS resource record type codes as well as for each
individual code. The URN for the list might look like this:
urn:ietf:params:dns:rr-type-codes
while the URN for the SOA records type code might look like this:
urn:ietf:params:dns:rr-type-codes:soa
Relevant ancillary documentation:
[3], [2], [1]
Identifier uniqueness considerations:
The IESG uses the IETF consensus process to ensure that
sub-namespaces generate unique names within that
sub-namespace. The IESG delegates to the IANA the task of
ensuring that the sub-namespace names themselves are unique.
Until and unless the IESG specifies differently, the IANA is
directed to ensure uniqueness by comparing the name to be assigned
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RFC 3553 IANA URN Namespace June 2003
with the list of previously assigned names. In the case of a
conflict the IANA is to request a new string from the registrant
until the conflict is resolved.
Identifier persistence considerations:
Once a name has been allocated it MUST NOT be re-allocated for a
different purpose. The rules provided for assignments of values
within a sub-namespace MUST be constructed so that the meaning of
values cannot change. This registration mechanism is not
appropriate for naming values whose meaning may change over time.
If a value that changes over time the assignment MUST name the
container or concept that contains the value, not the value
itself. For example, if a parameter called 'foo' has a value that
changes over time, it is valid to create the name
'urn:ietf:params:foo-params:foo' that identifies that 'slot'. It
is not valid to actually create a name that contains that value
unless it is a persistent and unique value such as a version
number.
Process of identifier assignment:
Identifiers are assigned only after a particular protocol element
or number has been registered with the IANA using standard
policies and procedures, or documented in an RFC describing a
standards track protocol. This means that the 'gating' function
for assignment is the "IETF Consensus" process documented in RFC2434 [4].
Process of identifier resolution:
At this time no resolution mechanism is defined.
Rules for Lexical Equivalence:
Lexical equivalence is achieved by exact string match according to
the rules for URN syntax found in RFC 2141 [1]. Specifically, due
to the URN syntax definitions, the 'stringprep' standard found in
RFC 3454 [7] does not apply.
Conformance with URN Syntax:
There are no additional characters reserved.
Validation mechanism:
None.
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RFC 3553 IANA URN Namespace June 2003
Scope:
Global
4. Assigning Names
The creation of a new registry name will be simple for most flat
registries. The only required elements will be the registry name, a
reference to relevant documents, a statement about which
current/proposed document repositories contains the authoritative
data for the registry, and a statement specifying which element in
the registry is the value to be used in the URN. In most cases this
last element will be the index value assigned by the IANA.
More complex registries (DNS Parameters for example) will need to
repeat that information for any sub-namespaces. It should also be
clear as to whether or not a name is assigned to the sub-namespace
itself (i.e., is 'urn:ietf:params:dns:rr-types' valid by itself and
if so, what does it name?).
The template:
Registry name: -- The name of the sub-namespace. In many cases this
should be the same name that the IANA calls the registry itself.
Specification: -- Relevant IETF published documents that define the
registry and the items in it.
Repository: -- A pointer to the 'current' location of the registry in
the protocol parameters repository or the relevant RFCs that
document the items being named. This value will change over time
as the entity that maintains the repository moves files and or
fileservers. It is not meant as a permanent binding to the
filename but as a hint to the IANA for what the initial mapping
would be.
Index value: -- Description of how a registered value is to be
embedded in the URI form. This MUST include details of any
transformations that may be needed for the resulting string to
conform to URN syntax rules and any canonicalization needed so
that the case-sensitive string comparison yields the expected
equivalences.
The process for requesting that a URN be assigned is currently to put
the above template or a reference to it in the IANA considerations
section of the specifying document. Other more automated processes
may be proposed at a latter time if demand requires it.
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RFC 3553 IANA URN Namespace June 20035. Security Considerations
None not already inherent to using URNs. Security considerations for
URNs in general can be found in RFC 2141 [1]. Further security
considerations for one specific URN resolution method can be found in
Dynamic Delegation Discovery System (DDDS) Part Four: The Uniform
Resource Identifiers (URI) Resolution Application (RFC 3404) [5]
which is part of a series starting with Dynamic Delegation Discovery
System (DDDS) Part One: The Comprehensive DDDS (RFC 3401) [6].
6. IANA Considerations
This document puts a new and significant burden on the IANA since it
may require an additional assignment process to happen for each new
IANA registry. To minimize the administrative burden on IANA, any
parameter namespace registration is very clear about the criteria for
inclusion in that namespace.
Defining a registry that fits the constraints of a URN namespace will
impose extra discipline that should take some of the guess-work about
creating and maintaining that registry.
7. Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances of
licenses to be made available, or the result of an attempt made to
obtain a general license or permission for the use of such
proprietary rights by implementors or users of this specification can
be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.
Mealling, et. al. Best Current Practice [Page 5]

RFC 3553 IANA URN Namespace June 200310. Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
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included on all such copies and derivative works. However, this
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The limited permissions granted above are perpetual and will not be
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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